Systematic on-site testing for SARS-CoV-2 infection among asymptomatic essential workers in Montréal, Canada: a prospective observational and cost-assessment study

Jonathon R. Campbell; Cynthia Dion; Aashna Uppal; Cedric P. Yansouni; Dick Menzies

doi:10.9778/cmajo.20210290

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Figure 1:
Flow diagram showing selection of businesses and participants.
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Figure 2:
Evolution of SARS-CoV-2 infection outbreaks at businesses A (A) and B (B) (both manufacturing and supplier sector).

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Table 1:

Characteristics of included businesses in Montréal-North

Characteristic	No. (%) of businesses n = 69	No. (%) of participants n = 2128
Business sector
Manufacturing/supplier	19 (27.5)	1225 (57.6)
Auto sales and repair	12 (17.4)	242 (11.4)
Childcare	11 (15.9)	113 (5.3)
Public services	8 (11.6)	144 (6.8)
Grocery	6 (8.7)	100 (4.7)
Retail	6 (8.7)	84 (3.9)
Construction	4 (5.8)	28 (1.3)
Meat processing	2 (2.9)	183 (8.6)
Legal	1 (1.4)	9 (0.4)
Size, no. of participants
1–5	11 (15.9)	44 (2.1)
6–10	14 (20.3)	113 (5.3)
11–20	26 (37.7)	388 (18.2)
21–50	10 (14.5)	350 (16.4)
≥ 51	8 (11.6)	1233 (57.9)

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Table 2:

Characteristics of participants

Characteristic	Test result; no. (%) of participants^*
Characteristic	Overall n = 2128	Positive n = 53	Negative n = 2075
Age, median (IQR), yr	48 (37–57)	49 (40–58)	48 (37–57)
Sex
Female	808 (38.0)	9 (17.0)	799 (38.5)
Male	1320 (62.0)	44 (83.0)	1276 (61.5)
Self-reported ethnicity
White	926 (43.5)	4 (7.5)	922 (44.4)
Asian	444 (20.9)	17 (32.1)	427 (20.6)
Black	295 (13.9)	21 (39.6)	274 (13.2)
Hispanic	204 (9.6)	6 (11.3)	198 (9.5)
Indigenous	4 (0.2)	0 (0.0)	4 (0.2)
Mixed	17 (0.8)	0 (0.0)	17 (0.8)
Other/not disclosed	238 (11.2)	5 (9.4)	233 (11.2)
Employment status
Full-time	2018 (94.8)	51 (96.2)	1967 (94.8)
Part-time or occasional	110 (5.2)	2 (3.8)	108 (5.2)
Reported health factor
Any^†	447 (21.0)	8 (15.1)	439 (21.2)
Hypertension	214 (10.0)	4 (7.5)	210 (10.1)
Diabetes	151 (7.1)	4 (7.5)	147 (7.1)
Chronic respiratory condition	64 (3.0)	1 (1.9)	63 (3.0)
Heart disease	31 (1.4)	0 (0.0)	31 (1.5)
Other	99 (4.6)	1 (1.9)	98 (4.7)
None	1681 (79.0)	45 (85.)	1636 (78.8)
Reported smoking
Never smoker	1668 (78.4)	46 (86.8)	1622 (78.2)
Current smoker	331 (15.6)	5 (9.4)	326 (15.7)
Former smoker	129 (6.1)	2 (3.8)	127 (6.1)
Previous SARS-CoV-2 test history^‡
Never tested	1155 (54.3)	42 (79.2)	1113 (53.6)
All test results negative	882 (41.4)	9 (17.0)	873 (42.1)
Any test result positive	91 (4.3)	2 (3.8)	89 (4.3)
Feeling on day of testing^§
“Fine, same as any other day”	2098 (98.6)	51 (96.2)	2047 (98.6)
“Not my best today”	30 (1.4)	2 (3.8)	28 (1.3)
Business sector
Manufacturing/supplier	1225 (57.6)	43 (81.1)	1182 (57.0)
Meat processing	183 (8.6)	6 (11.3)	177 (8.5)
Childcare	113 (5.3)	3 (5.7)	110 (5.3)
Other	607 (28.5)	1 (1.9)	606 (29.2)
Business size, no. of participants
1–5	44 (2.1)	1 (1.9)	43 (2.1)
6–10	113 (5.3)	2 (3.8)	111 (5.3)
11–20	388 (18.2)	1 (1.9)	387 (18.6)
21–50	350 (16.4)	0 (0.0)	350 (16.9)
≥ 51	1233 (57.9)	49 (92.4)	1184 (57.1)

Note: IQR = interquartile range.
↵* Except where noted otherwise.
↵† Participants could have more than 1 health factor.
↵‡ Before enrolment in the study.
↵§ As reported on patient questionnaire.

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Table 3:

Cost per person tested of training, scheduling, saline gargle collection, sample transport and contacting of participants, assuming two 50-person businesses are visited per day by 2 mobile team members

Cost	Cost per person tested, $	Details
Laboratory	34.00	Reimbursement cost for RT-PCR to detect SARS-CoV-2
Nonlaboratory	8.67
Training mobile team	0.04
Coordinator and mobile team personnel	0.03	Based on 2 d of training^*
Materials and refreshments	0.01	Includes meals, materials for sample collection, and sanitizing and personal protective equipment^†
Administrative personnel to schedule businesses	0.80	Based on 2 h per business^‡
Sample collection	5.62
Mobile team personnel	2.99	Based on 45 min to set up and tear down at each business and 6 min per person tested^‡
Sanitizing materials	0.33	Includes rags, paper towels, disinfectant and hand sanitizer^†
Personal protective equipment	0.38	Includes 4 masks per day and 2 gloves per participant^†
Sample collection materials	1.74	Includes a sample tube, a 5-mL saline ampoule and 2 biohazard bags^†
Capital purchases	0.18	Includes items such as chairs, tables, trash bins, Plexiglass dividers, stationery, tablets for data collection, storage bins, dollies and coolers^†
Sample transport	0.54
Mobile team personnel	0.19	Assuming 30 min to drop off samples and 10 min driving between businesses^‡
Vehicle and fuel	0.35	Assuming 60 km driven per day^‡
Administrative personnel to communicate results	1.67	Based on 5 min per result on average^‡
Total	42.67

Note: RT-PCR = reverse transcription polymerase chain reaction.
↵* Estimated during study for nonresearch training days.
↵† See Appendix 1, Table S2, for more details.
↵‡ Estimated during study.

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Table 4:

Logistic regression results for factors potentially associated with ever testing positive^*

Factor	No. of participants n = 2128	No. (%) of tests positive	Adjusted OR (95% CI)^†
Age (per 1-yr increase)	–	–	1.0 (0.98–1.0)
Sex
Female	808	9 (1.1)	1.0 (reference)
Male	1320	44 (3.3)	2.2 (0.9–5.3)
Self-reported ethnicity
White	926	4 (0.4)	1.0 (reference)
Nonwhite	1202	49 (4.1)	3.7 (1.4–9.9)
Health factor^‡
None reported	1681	45 (2.7)	1.0 (reference)
Any reported	447	8 (1.8)	0.7 (0.3–1.5)
Smoking history
Never smoker	1668	46 (2.8)	1.0 (reference)
Current or previous smoker	460	7 (1.5)	0.7 (0.3–1.5)
Feeling on day of testing
“Fine, same as any other day”	2098	51 (2.4)	1.0 (reference)
“Not my best today”	30	2 (6.7)	3.5 (0.7–16.9)
Previous SARS-CoV-2 test history
Never tested	1155	42 (3.6)	1.0 (reference)
All test results negative	882	9 (1.0)	0.4 (0.2–0.8)
Any test result positive	91	2 (2.2)	0.7 (0.2–3.0)
Business size, no. of participants
1–50	895	4 (0.4)	1.0 (reference)
≥ 51	1233	49 (4.0)	7.9 (0.8–75.3)

Note: CI = confidence interval, OR = odds ratio.
↵* The model accounts for clustering by business and sector.
↵† Models are adjusted for all factors included in the table.
↵‡ Includes hypertension, diabetes, chronic respiratory conditions (e.g., asthma), heart disease or participant-reported condition.